The present invention relates to cementing operations, and more particularly, to cement compositions comprising environmentally compatible defoamers and methods of using such cement compositions.
Hydraulic cement compositions commonly are utilized in subterranean operations, particularly subterranean well completion and remedial operations. For example, hydraulic cement compositions may be used in primary cementing operations, whereby pipe strings such as casings and liners are cemented in well bores. In performing primary cementing, hydraulic cement compositions may be pumped into an annular space between the walls of a well bore and the exterior surface of a pipe string disposed therein. The cement composition is permitted to set in the annular space, thereby forming therein an annular sheath of hardened substantially impermeable cement that substantially supports and positions the pipe string in the well bore, and bonds the exterior surface of the pipe string to the walls of the well bore. Hydraulic cement compositions also are used in remedial cementing operations that involve plugging highly permeable zones or fractures in well bores, plugging cracks and holes in pipe strings, and the like.
Hydraulic cement compositions often comprise defoaming compositions, or “defoamers.” Defoamers commonly are utilized, for example, as components in well treatment fluids to prevent the formation of foam or the entrainment of gas during the preparation and placement of the well treatment fluid in the subterranean formation. Defoamers also have been utilized for “breaking” foamed fluids. For example, when an operator desires to dispose of a foamed well treatment fluid aboveground, the operator may add a defoamer to the well treatment fluid to break the foam, and thereby facilitate disposal of the well treatment fluid. Defoamers often are included in cement compositions, inter alia, to ensure proper mixing and to provide adequate control over the density of the cement composition.
A variety of defoamers are well known in the art, some of which may have undesirable environmental characteristics and/or may be limited by strict environmental regulations in certain areas of the world. Furthermore, many defoamers that comply with these strict environmental regulations may be relatively expensive and/or may suffer from other drawbacks, such as poorer defoaming performance.